Method of assembling target and backing plates

ABSTRACT

A low temperature target and backing plate bonding process and assemblies made thereby. A plurality of male projections ( 8 ) are formed in one member ( 2 ) of the assembly with a plurality of corresponding female recesses ( 9 ) formed in the other member ( 4 ). The assembly is bonded by conventional techniques around the peripheral boundary ( 25 ) that surrounds the male and female portions ( 8,9 ). The assembly is then pressure consolidated at low temperature so that the projections ( 8 ), circumscribed by the bonded zone, are force fit into the female recesses ( 9 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority filing benefit of (1) International PCT applicationPCT/US00/18968 filed Jul. 12, 2000, and published under PCT 21(2) in theEnglish language and (2) U.S. provisional application Ser. No.60/143,314 filed Jul. 12, 1999.

BACKGROUND OF THE INVENTION

The present application pertains to a low temperature sputtertarget/backing plate joining technique and to assemblies made thereby.

In my U.S. provisional patent applications No. 60/099,981, filed Sep.11, 1998 and No. 60/129,559, filed Apr. 16, 1999, a target and backingplate are provided wherein the harder material of the two is machined orotherwise formed so as to have a plurality of ridges or other salientsurface portions thereof. These ridges or salient portions are formedalong the interior surface of the target or backing plate. The ridgedsurface is then placed alongside the mating surface of the other memberof the assembly along the target/backing plate interface wherein joiningwill occur.

The peripheral portion of the interfacial surface assembly, surroundingthe ridges or salient portions, is joined by conventional means such aselectron beam welding, TIG welding, friction welding, soldering,brazing, etc., preferably under vacuum. The assembly is then pressed ata low temperature, preferably at room temperature.

The projections or ridges formed along either the target or backingplate bend upon penetration into the mating metal surface along thetarget/backing plate interface and form an interlocking grip over thesofter metal on the opposing mating surface.

SUMMARY OF THE INVENTION

In this invention, a target and backing plate are provided wherein bothmaterials are similar in mechanical properties and both are machined orotherwise formed so as to have a plurality of ridges and grooves orother salient surface portions thereof. These ridges or salient portionare formed along the interior surface of the target or backing plate.The ridged surface is then placed alongside the mating surface (havingappropriately positioned mating members) of the other member of theassembly along the target/backing plate interface wherein joining willoccur.

The peripheral portion of the interfacial surface assembly is joined byconventional means such as electron beam welding, TIG welding, frictionwelding, soldering, brazing, etc., preferably under vacuum. The assemblyis then pressed at a low temperature, preferably at room temperature.

The projections or ridges formed along either the target or backingplate penetrate into the mating members along the target/backing plateinterface. The projections penetrate into the grooves on the opposingmating surface.

The projections and grooves have different sizes so that afterpenetration, a force or friction fit joint will be formed.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of a target and backing plateassembly showing the friction fit joining mechanisms in the form ofcylindrical male projections ready for insertion into cylindrical bores;

FIG. 2 is a schematic cross section showing another embodiment of thejoining members having square male projections in one member andcorrespondingly square shaped recesses formed in the other member,

FIG. 3 is a schematic cross sectional view of the assembly shown in FIG.1 in the mating or joined position;

FIG. 4 is a schematic cross sectional view of the assembly shown in FIG.2 in the mating or joined position;

FIG. 5 is a partially exploded perspective view of the assembly of FIG.1 before bonding, and

FIG. 6 is a partially exploded perspective view of the assembly of FIG.2 before bonding.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning first to FIG. 1 there is shown a target/backing plate assembly.The assembly comprises a target 2 having a top side 23 carrying metal ormetal alloy that, in accordance with conventional sputtering methods,will be ejected from the target via ionic bombardment and will travel toand coat the desired substrate.

A backing plate 4 is provided under the target, with the bottom side 11of the target adapted to mate with the top side 13 of the backing plateto define an interfacial surface area 28. Commonly, a heat exchangefluid such as water is circulated adjacent the bottom side 21 of thebacking plate so as to cool the assembly during its sputteringoperation.

As shown in the FIG. 1 embodiment a plurality of cylindrical maleprojections 8 are machined into the surface 11. The surface 13 isprovided with cylindrical female bore members 9 of smaller diameter thanthe diameter of the male projections 8.

In some cases, it is desired to provide a filler material 6, such as anAl 4%Si alloy or other suitable alloy, in the form of a ring or thelike, adjacent the peripheral border 25 of the assembly between thetarget and backing plate. The filler material 6 enhances bonding of thetarget to the backing plate as shall be explained hereinafter.

The assembly is first bonded around the peripheral border 25. Thisinitial bonding along the peripheral border of the assembly may beachieved by conventional means such as by E-beam welding under vacuumconditions, TIG welding, and friction welding and the like. Preferably,the bonding of the peripheral boundaries of the target and backing plateis performed via E-beam welding under vacuum conditions.

After the peripheral bonding, the assembly is consolidated, via pressureapplication thereto, at pressure of about 50 tons-5,000 tons; preferablyless than about 1,000 tons, under low temperature conditions. The malemembers 8 are friction fit into the corresponding female bores 9.

After the low temperature pressure consolidation, the assembly may besubjected to a low temperature annealing step conducted at temperaturesof about room to 400° C. for a period of 0.5 to 4 hours. This will helpensure adequate adhesion of the pressure consolidated surfaces.

The phrase “low temperature pressure consolidation” refers to pressureconsolidation that may occur at temperatures of less than about 50% ofthe melting temperature of the lower melting member of the target andbacking plate. Preferably, this temperature is less than about 200° C.;most preferably at about room temperature up to about 38° C.

Turning now to FIG. 2, there is shown another embodiment of theinvention wherein the target and backing plate may be joined by lowtemperature pressure consolidation. Here, the male projections 8 are inthe form of elongated square cross sectioned members that are force fitinto square recesses 9 formed in the backing plate 4.

FIGS. 3 and 4 show the assemblies of FIGS. 1 and 2 respectively in theirmated positions in which, by reason of the low temperature pressureconsolidation, the projecting male members are frictionally free fit intheir mating, female recesses and in which the target and backing plateare bondingly joined.

FIG. 5 shows, in perspective, the male and female coupling members ofthe FIG. 1 embodiment. Male members 8 are in the form of a cylindricaldowel-like projection adapted for mating with the cylindrical bores 9.The bores 9 have a smaller id than the od of the projecting male members8. As shown, the male members 8 and the bores 9 are arranged in apattern of concentrically arranged annular rows.

FIG. 6 depicts the male/female mating members shown in the FIG. 2embodiment. Here, the male members 8 are in the form of elongated squarecross-sectioned studs adapted for reception into the smaller openings 9.

In one target/backing plate assembly bonding in accordance with theinvention, rectangular cross-sectioned male projections were used andfrictionally fit into corresponding rectangular female openings. Thetarget and backing plate were both copper and the female openings wereabout 0.010″ smaller than the male members. The male and female memberswere machined into the respective surfaces. The target/backing plateassembly was pressed so that the male and female coupling members werefriction fit. After pressing, the peripheral portion of the assembly waswelded via electron beam. After the welding step, a final machiningoperation was performed so that the welded area was not removed.

The locking joint of the invention can therefore be described as afriction fit joint formed between a projecting male member disposed onone member and a corresponding female opening formed in the othermember.

While the methods described herein, and the target/backing plateassemblies produced in accordance with the methods, have been describedwith certain specific forms and certain modifications thereof, it willbe appreciated that a wide variety of other modifications can be madewithout departing from the scope and spirit of this invention as definedin the appended claims. It is also to be kept in mind that reference toa metal or metal component herein also includes reference to alloyedforms of the stated metal.

Although copper to copper bonding is specifically mentioned, othermetals can benefit from the invention. For example, Al target to Albacking plates may be joined using the methods herein disclosed. Othertarget to backing plate combinations are possible provide the mechanicalcharacteristics of the metals such as hardness and thermal expansion,are similar.

The present invention provides advantage over diffusion bonding andother joining techniques that require higher temperatures in theconsolidation. Higher temperature conditions sometimes result inundesirable grain growth in the target metal.

What is claimed is:
 1. In a method of preparing a bonded sputtertarget/backing plate assembly comprising a target composed of a metal oralloy to be sputtered and an underlying metallic backing plate member,an improved method for joining said target and backing plate alongmating surfaces thereof, comprising: a) forming a plurality ofprojecting male portions in at least one of said mating surfaces and aplurality of female recesses in said other of said mating surfaces; b)positioning said target and backing plate adjacent each other to form anassembly having an interface defined by said mating surfaces; and c)pressure consolidating said assembly under low temperature conditions ofless than about 38° C. whereby that said male portions force fit intosaid female recesses to bondingly join said target and backing plate toeach other.
 2. Method as recited in claim 1 wherein said assemblyincludes a peripheral boundary surrounding said male projections andsaid female recesses and further comprising the additional step of (d)bonding said assembly proximate the peripheral boundary of saidassembly.
 3. Method as recited in claim 2 wherein said step (d) isperformed after said step (b) and before said step (c).
 4. Method asrecited in claim 3 wherein said step (d) comprises e-beam welding ofsaid assembly.
 5. Method as recited in claim 4 wherein said step (d)further comprises interposing a weldable filler material between saidtarget and said backing plate proximate said peripheral boundary. 6.Method as recited in claim 2 wherein said step (d) comprises frictionwelding.
 7. Method as recited in claim 2 wherein said step (d) comprisesTIG welding.
 8. Method as recited in claim 6 wherein said targetcomprises Cu.
 9. Method as recited in claim 2 wherein said step (d)comprises e-beam welding said target along an annular zone locatedadjacent said peripheral boundary.
 10. Method as recited in claim 2further comprising (e) low temperature annealing said pressureconsolidated assembly.
 11. Method as recited in claim 1 wherein saidstep (c) comprises pressure consolidating said assembly at about roomtemperature.
 12. Method of bonding a sputter target to a backing platemember along a plane defined by mating interfacial surfaces of saidtarget and backing plate, said method comprising: a) forming a pluralityof projecting male portions in one of said interfacial surfaces, and aplurality of female recesses in said other of said mating surfaces; b)positioning said target and backing plate in a position ready forbonding with said interfacial surfaces adjacent each other; and c)pressure consolidating said target and backing plate at a temperature ofless than about 38° C. and at a pressure sufficient to force fit saidmale projections into said female recesses to bondingly join said targetand backing plate to each other.
 13. Method as recited in claim 12wherein said step (c) is conducted at about room temperature.
 14. Methodas recited in claim 13 wherein said target is Cu or Cu alloy.
 15. Methodas recited in claim 13 further comprising, prior to said step (c), astep (d) of bonding said target and backing plate member around aperipheral boundary portion of said mating interfacial surfaces. 16.Method as recited in claim 15 wherein said step (d) comprisesinterposing a weldable filler material between said target and saidbacking plate along said peripheral boundary portion.
 17. Method asrecited in claim 15 wherein step (d) comprises e-beam welding. 18.Target/Backing plate assembly made by any one of the preceding claims.